Resinous condensation products of furylethylene derivatives and aldehydes



Patented Oct. 31, 1950 RESINOUS CONDENSATION PRODUCTS OF FURYLETHYLENEDERIVATIVES AND ALDEHYDES Andrew P. Dunlop, Riverside, and Ernest L.Washburn, Wilmette, Ill., assignors to The Quaker Oats Company, acorporation of New Jersey No Drawing. Application November 1, 1946,Serial No. 707,335. In Canada September 16, 1946 10 Claims.

This invention relates to novel synthetic resins of the thermosettingtype which are formed by reacting formaldehyde, a compound whichengenders formaldehyde, or glyoxal with a furylethylene derivativehaving a terminal monovalent radical selected from the class consistingof H, alkyl, aryl, CHO, COOH, COOR, CN and N02. These resins are capableof being manufactured economically into useful articles under readilycontrolled conditions.

This application is a continuation-in-part of our copending applicationSerial No. 628,990, filed November 15, 1945.

The resins prepared in accordance with our invention may be used aloneor together with other resinous bodies in the preparation of solutionsfor impregnatingv and laminating purposes, in the preparation ofprotective coatings and varnishes, for the formation of molded articlesand.

for other uses which will be apparent to those skilled in the art. Inconnection with the preparation of molded articles, these resins may becompounded in molding powder form with suitable fillers.

In carrying out the process of the present invention a furylethylenederivative of the type referred to above and described in greater detailbelow is condensed with formaldehyde or with a compound which engendersformaldehyde such as paraformaldehyde, trioxymethylene, and trioxane, orwith glyoxal, or with a mixture of such compounds, inthe presence of anacidic catalytic agent. In many instances the condensation reaction maybe carried out under reflux conditions at the reflux temperature of thereactants, but in some instances higher temperatures are required. Ingeneral, the reaction is eifected at an elevated temperature in theorder of about 75-140 C., or at higher temperatures, in about one-halfto four hours. The reaction proceeds rapidly in an aqueous acid medium.The rate of reaction is, in general, more rapid at the highertemperatures and/or at a relatively low pH. Prior to the condensationthe furylethylene derivative may, if required and if desired, be Washedto remove water soluble materials, or it may be distilled to removewater and other volatile products.

The ratio of the compound having active methylene groups or of theglyoxal to the furylethylene derivative in the reaction mixture may bevaried over a wide range, for example from about 0.5 to about 3.0 molsof the former per mol of the latter.

The materials formed in accordance with this reaction are usuallyviscous, black resins. In some instances they are fusible solids and inothers they are dark-red tacky resins. They can be converted by heat, inthe presence or absence of acidic or basic curing accelerator orcatalysts, into insoluble, infusible products. The use of curing agentsis preferred not only because they accelerate the rate of cure butbecause in some instances they promote an improved yield of insoluble,infusible product. In the case of the viscous fluid resins, theformation of the infusible, insoluble product proceeds through a rubberyel state into the final solid state.

The uncured resins are generally soluble in common organic solvents suchas acetone, dioxane and ethyl acetate.

The furylethylene derivatives which are usedin. accordance with thepresent invention have the general formula HooH wherein X is a member ofthe class consisting of hydrogen and a monovalent hydrocarbon radical, nis an integer and Y is a monovalent radical selected from the groupconsisting of H, alkyl, aryl, CHO, COO'I-I, COOR, CN and N02. r

The preferred resins in accordance with th present invention are formedwhen the furylethylene derivative is a compound having the above generalformula where the terminal group is CHO. These compounds may be preparedby reacting furfural With an aldehyde having at least one carbon atomwhich has thereon atleast two active hydrogen atoms such asacetaldehyde, propionaldehyde, butyraldehyde, crotonaldehyde,phenylacetaldehyde and the like or mixtures thereof. In general,aldehydes having at least two active hydrogen atoms are thosealdehydeshaving at least two hydrogen atom on acarbon atom in the alphaposition to the aldehyde group or unsaturated aldehydes having activehydrogen atoms due to the influence of a carbon to carbon double bond.

The methods of preparing the simple furylethylene derivatives of theabove general formula where the terminal group is 01-10 are well knownas are also the methods of preparing the higher homologs.

- prepared by reacting furfural with mixtures, of

These higher homologs have been' active hydrogen atoms. Furylethylenederivatives having a terminal aldehyde group have been prepared byprogressive condensations of furfural or furylacrolein with acetaldehydeor crotonaldehyde up to the relatively high molecular weight homolog,15(a-furyl)-pentadecaheptaenal, wherein X=hydrogen and 11:7 (refer togeneral formula above). Schmitt: Ann. 5 17, 270 (1941) and Konig: Ber.58, 2559 (1925). Such condensations are, of course, not peculiar tofurfural, but are shown by aldehydes in general when reacted with otheraldehydes possessing active hydrogen atoms. The mechanism is probablyone of aldolization followed by loss of water to form an ethylenicdouble bond. The simplest ilulstration is the condensation ofacetaldehyde with itself to form aldol. By loss of water, aldol yieldscrotonaldehyde which contains an ethylenic double bond.

A Wide variety of catalysts have been used more or less successfully incarrying out such condensations. These include: (1) alkali metalhydroxides, carbonates, acetates and cyanides, (2) those of theFriedel-Crafts type (A1013, BFs, etc), (3) tertiary amines(dimethylaniline, triethanolamine, etc.) and (4) piperidine acetate.Zinc chloride and in some cases acids have also been used to effect suchcondensations. Any of these catalysts may be employed in preparing thefurylethylene derivatives having a terminal aldehyde group which are thepreferred starting materials of this invention. For reasons of economyand convenience, however, we prefer to use as catalysts, alkali metalhydroxides such as NaOI-I or alkali metal carbonates such as NazCOs.

We prefer to carry out the condensation reaction'of furfural and analdehyde, etc., to form the preferred starting materials of the presentinvention, at low temperatures, in the order of -15 C., for'example. Athigher temperatures, (in the neighborhood of reflux) there is a tendencyfor condensation to yield complex mixtures due to side reactions and themixture, though useful for our purposes, is somewhat less satisfactorythan the products obtained at low temperatures. It is preferred to carryout the condensation reactions in an aqueous medium but an organicsolvent may be employed, if desired, for example methanol. The productsobtained at low or high temperatures and in aqueous or alcoholic mediumhave been found useful in preparing the novel resins of this invention.

Examples 1 to 5 are illustrative of methods of preparing the preferredstarting materials in accordance with the present invention. In theseillustrative examples sodium hydroxide is used, for convenience, as thecondensing agent, but the other condensing agents may, of course, alsobe used. In each of the examples in this application, parts indicatedare parts by weight.

Example 1 Preparation of furylacrolein: A solution containing 384 parts(4 mols) furfural and 193 parts (4+ mols) acetaldehyde (excess ofaldehyde to cover evaporation losses) was slowly added over a period of5 hours to a stirred solution of 30 parts of sodium hydroxide in 1000parts of Water in which 500 parts of ice cubes were suspended. Theresulting mixture was adjusted to a pI-I of 7 with sulfuric acid afterwhich the two layers which formed were separated. The bottom layer wasdried by vacuum distillation to yield crude furylacrolein (416 parts or85 per cent of theoretical). The crude furylacrolein of the example Willhereafter be referred to as furylacrolein C.

Example -2 Furylpentadienal C was prepared from furfural andcrotonaldehyde in a manner similar to the method of preparingfurylacrolein C. The yield of furylpentadienal C was 8'7 per cent oftheoretical. The product, prior to drying, is referred to as wetfurylpentadienal C.

Example 3 Furylacrolein C plus acetaldehyde: A solution containing 30.5parts (0.25 mol) furylacrolein C and 12 parts (025+ mol) acetaldehydewas added over a period of 15 minutes to a stirred solution of 2 partssodium hydroxide in 10 parts water and parts methanol at 15 C. Afterstirring for an additional 30 minutes the mixture was neutralized with10 per cent sulfuric acid and vacuum distilled to remove the methanol.Sodium sulfate was removed by washing with Water and the residue wasdried under vacuum to yield about 35 parts of sticky, viscous liquid,which crystallized on standing overnight.

Example 4 Furylpentadienal C plus crotonaldehyde: A solution containing37 parts (0.25 mol) furylpentadienal C and 17.5 parts (0.25 mol)crotonaldehyde was theated the same as in Example 3 to yield 45 parts ofa very viscous, black product.

It is manifest that propionaldehyde and higher hornologs may be used inplace of or in admixture with acetaldehyde or crotonaldehyde to yieldunsaturated aliphatic aldehydes with terminal furyl groups. Thus, forexample, propionaldehyde reacted with furfural .yields Ho( n1 n CH3 H|CC=(]JCHO and this compound reacted with additional propionaldehydeyields t l 1 HC co H (llHzH CH3 Additionally, phenylacetaldehyde reactedwith furfural yields [a-phenyl-fiQ-furyl) acrolein] HCCH H CsH5 Similarproducts may be obtained from the higher homologs of phenylacetaldehyde,including products where the X of the above general formula is anaralkyl radical.

Example 5 .brought to pH 6 by addition of dilute HCl.

tions of water. This yielded 35.7 parts of a brown, oily liquid fromwhich about 14 parts of the pure compound, B. P. 166-177 C./7.5 mm. ('n1.651), were obtained by fractional distillation.

The compound was also prepared as follows. To a similar solution ofphenylacetaldehyde and furfural there was added over a period of 1 hour,a solution of sodium methoxide (2 parts Na metal dissolved in 25 partsmethanol). The mixture was stirred and maintained at 15-20 C. for atotal of 7 hours at which time it was On Working this material up in thesame manner as above there were obtained 16 parts of the pure compound,B. P. 144-155 0. /3 mm. (no 1.644).

The pure products crystallized on standing. They were mixed and reactedwithformaldehyde to form a resin as described in Example 10.

Any aldehyde having at least two hydrogen atoms on a carbon atom in thealpha position to the aldehyde group or an unsaturated aldehyde havingactive hydrogen atoms due to an unsaturated carbon to carbon bond may besubstituted for acetaldehyde in Example 3 or for crotonaldehyde inExample 4. Thus, for example, crotonaldehyde may be used in lieu of theacetaldehyde of Example 3 and acetaldehyde in lieu of the crotonaldehydeof Example 4.

The following examples illustrate the preparation of resinous productsfrom furylethylene derivatives having a terminal aldehyde group.

Example 6 731 parts (6 mols) furylacrolein C, 486 parts formalin (6 molsCHzO) and 28 parts of concentrated hydrochloric acid were placed in aflask fitted with a reflux condenser and heated at about 80 C., whilestirring, for a period of 37 minutes. At this time the reaction mixturewas cooled and adjusted to a pH of 7 with sodium carbonate. The mixturestratified into two layers. These were separated and the resin layer waswashed several times with cold water. 8'79 parts of a wet, viscous,black resin were obtained. On curing this resin for 20 hours at 110 C.followed by six hours at 190 C., a solids yield of 53 per cent wasobtained. This yield was increased to 59 per cent by curing in thepresence of 4 per cent hexamethylenetetramine or 1 per cent sodiumhydroxide. In each case, the cured product was a hard, shiny black,infusible and insoluble resin.

Example 7 740 parts (5 mols) furylpentadienal C, 406 parts of formalin(5 mols CHzO) and 18 parts concentrated hydrochloric acid were heated ina manner similar to that employed in Example 6. The reaction mixture wasmaintained at 85- 90 C. for 25 minutes, after which it was cooled andneutralized with sodium carbonate. After washing with water there wasobtained 913 parts of a Wet, viscous, black resin. The solids yield oncuring as above was 62 per cent.

Example 8 17.7 parts of the product of Example 3, 20.8 parts formalin(7.5 parts CHzO) and 2.5 parts of 2.4 normal hydrochloric acid wereheated under reflux on a steam bath for one hour which treatment carriedthe resin through the viscous stage to a rubbery gel. The solids yieldon curing as above was 81.2 per cent based on the weight of thereactants.

Example 9 Example 10 w 5 parts (0.025 mol) of the mixed product ofExample 5, 4.05 parts of formalin (0.05 mol CHzO) and about 1 part of 6N HCl were treated on an oil bath under reflux conditions at l25 5 C.,for 4 /2 hours. At this time the bottom layer was a very viscous blackresin. On cooling it solidified toa grindable, fusible resin (5.86 partsafter washing and drying under vacuum) soluble in acetone, dioxane andethyl acetate, and insoluble in methanol in the cold. On heating aportion (2.0 parts) of this resin in an oven at 190i5 C., for 18 hours,there were obtained 1.70 parts of a cured product which was not quitehard when hot. When portions of this resin were heated in the presenceof HsPO4 and NaOH the cure was efiected much more rapidly.

The following examples illustrate the preparation of resinous productsin accordance with the present invention, from furylethylene derivativescorresponding to the above general formula where the terminal group is amonovalent radical other than an aldehyde.

Example 11 4.7 parts (0.05 mol) of Vinylfuran, 4.0 parts formalin (005+mol CI-IzO) and about 0.5 part of 2 N HCl were sealed in a glass tubeand heated for a total of two hours at -106 C. The resulting resin wastacky and had a darkred color. The tube was opened and the contents wereheated at 180-185 C. for 16 hours, yielding a dark-red, infusible resin.

Example -12 6.90 parts (0.05 mol) of furylacrylic acid, 4.0 partsformalin (005+ mol CHzO) and about 1 part of 6 N HCl were sealed in aglass tube and heated at 95106 C. for threehours and then at -140 C. forone hour. The tube was opened and the contents were heated at -185 C.for 16 hours, yielding a hard, black infusible resin.

Example 13 mass, were heated at 180-185 C. for 16 hours,

yielding a hard, black resin. The rubbery resin converted to the hardfinal form without melting initially.

Resins similar to those described in the foregoing examples are preparedby reacting other furylethylene derivatives with formaldehyde, glyoxal,eta, inthe presence of hydrochloric acid The tube was opened and the ior other acid catalyst, in accordance with the procedures describedabove. Thus, thermosetting resins are formed by condensing formaldehydewith furylacrylonitrile and esters of furylacrylic acid such as n-amylfuracrylate, n-butyl furacrylate, methyl furacrylate, ethyl furacrylate,etc., in the presence of hydrochloric acid.

as being 100 per cent. These represent the amount of CHzO reacted whenthe resin is carried to a solid stage. At the intermediate stages thevalue is less so that it may be advisable in using these resins in aviscous, fluid state to incorporate paraformaldehyde or the like withthe varnish or molding compound.

Total Cured Mols 011: Wet Furyl-Pcntadenial 0 Catalyst $333, 1 heating@fififif gggg gggg time Per Cent pcntadlenal C Mol Hours 19.7 parts 0125mol on dry basis BFa (1.1 parts) 0. 125 2 75. 5 0. 80 l)o i Oxalic acid(0.5 part) 0.125 4 72. 7 0.85 Do Maleic anhydride (0.5 part... 0.125 375. 5 0. 84

Similar resins are similarly prepared by condensing w-methyl-vinylfuran,w-phenyl-vinylfuran and like compounds with formaldehyde, glyoxal, etc.

The compound w-n-lethylvinylfuran was pre pared by reacting furfuralwith ethyl propionate, treating the resulting product with sodiumhydroxide to form a salt, acidifying the salt and then decarboxylatingit. The corresponding aryl compound was similarly prepared, using,however, ethyl phenylacetate, instead of ethyl propionate.

In accordance with our invention, the hydrochloric acid of the foregoingexamples may be replaced by sulfuric acid, phosphoric acid, borontrifluoride, oxalic acid and maleic acid. In general, it was found thatthe rate of reaction was increased by increasing the concentration ofthe catalyst. With phosphoric acid as the catalyst, the best results areobtained at reaction temperatures above about 100 C.

The following is illustrative of some aspects of the inventionheretofore referred to.

Wet furylpentadienal C was reacted with formalin using differentmaterials listed in the table below as catalysts. The ingredients wereheated in sealed tubes at 110-145 C. and then the resulting productswere worked up to determine (a) unreacted formaldehyde, and (b) yield ofcured solids.

Ingredients:

mol equivalent of wet furylpentadienal C.

mol CHZO as formalin Catalyst as indicated in the table below. The tubeswere inspected every hour. When any particular composition hadprogressed to a solid state it was heated for one hour additional. Afterthis period each of the tubes was opened, the liquid portion (if any)poured off and the solid resin washed with water. Liquid and washingswere then analyzed for formaldehyde. The solid resin was dried, finelyground and a portion of the ground product was leached overnight withwater to dissolve any unreacted formaldehyde which was determined by thehydroxylamine-hydrochloride method. Blanks, with no formaldehyde added,were also run in The tubes were inspected every hour. When any order tocorrect for any water-soluble aldehydes that might have come from theunsaturated aldehyde having a terminal furyl group. The resultsnecessitated a correction of -0.2 to O.3 part in order to obtain a truevalue for the CH2O recovered. The cured solids yield was obtained byheating the ground resin at 120 C. for 6 hours. The values listed in thefollowing table are based on the furylethylene derivative having aterminal aldehyde group plus 01-120 In similar sealed tube experiments,where the mol ratio of CH2O:fury1pentadienal C was, respectively, 2:1and 3:1, the catalyst was HCl (8 cc. of 2.5 N HCl per molfurylpentadienal C) and the heating time was 2 hours, hard resins wereobtained which yielded 75% and 73.6%, respectively, of cured solids,usin the procedure described above. The mole of CH2O reacted per mol offurylpentadienal C were, respectively, 1.81 and 2.88. In theseexperiments where a 2:1 mol ratio of CHzO was used, one-half of the CHzOwas supplied as formalin and the other half as paraformaldehyde. Where a3:1 mol ratio of CH2O was used, one-third of the CHzO was supplied asformalin and the balance as paraformaldehyde.

Our invention is not to be construed as limited to the specificconditions, proportions and details set forth in the foregoingillustrative examples except insofar as such limitations are specifiedin the appended claims.

We claim:

1. A new artificial thermosetting resin comprising the product ofcondensation under acidic conditions of formaldehyde with afurylethylene derivative corresponding to the general formula wherein Xis a member of the class consisting of hydrogen and a monovalenthydrocarbon radical, n is an integer and Y is a monovalent radicalselected from the class consisting of H, alkyl, aryl, CHO, COOH, COOR,CN and N02, and wherein the R. of COOR is a monovalent alkyl radical, inthe proportion of about 0.5 to 3.0 mols of the aldehyde per mol of thesaid furylethylene derivative.

2. The new artificial thermosetting resin of claim 1 wherein X and n areas in claim 1 and Y is H.

3. The new artificial thermosetting resin of claim 1 wherein X and n areas in claim 1 and Y is alkyl.

4. The new artificial thermosetting resin of claim 1 wherein X and n areas in claim 1 and Y is aryl.

5. A new artificial thermosetting resin comprising the product ofcondensation under acidic conditions of glyoxal with a furylethylenederivative as designated in claim 1.

6. A new artificial thermosetting resin comprising the product ofcondensation under acidic conditions of a compound of the classconsisting of formaldehyde, compounds which engender formaldehyde andglyoxal with a furylethylene derivative corresponding to the generalformula wherein X is a member of the class consisting of hydrogen and amonovalent hydrocarbon radical, n is an integer and Y is a monovalentradical selected from the class consisting of H, alkyl, aryl, CHO,COOI-I, COOR, CN and N02, and wherein the R of COOR is a monovalentalkyl radical, in the proportion of about 0.5 to 3.0 mols of thealdehyde per mol of the said furylethylene derivative.

7. The method of making artificial thermosetting resins comprisingcondensing, in an acid medium, formaldehyde with a furylethylenederivative as designated in claim 6, until a resin is formed which iscapable of being converted to the infusible state under the influence ofheat, and then interrupting the condensation reaction.

8. The method of making artificial thermosetting resins comprisingcondensing, in an acid medium, glyoxal with a furylethylene derivativeas designated in claim 6, until a resin is formed which is capable ofbeing converted to the infusible state under the influence of heat, andthen interrupting the condensation reaction.

9. The method of making artificial thermosetting resins comprisingcondensing, in an acid medium, a compound of the class consisting offormaldehyde, compounds which engender formaldehyde and glyoxal with afurylethylene derivative as designated in claim 6, until a resin isformed which is capable of being converted in 10 the infusible stateunder the influence of heat, and then interrupting the condensationreaction.

10. A new artificial thermosetting resin comprising the product ofcondensation under acidic conditions of formaldehyde with afurylethylene derivative corresponding to the general formula wherein Xis a member of the class consisting of hydrogen and a monovalenthydrocarbon radical, and n is an integer, in the proportion of about 0.5to 3.0 mols o fthe aldehyde per mol of the said furylethylenederivative.

ANDREW P. DUNLOP. ERNEST L. WASHBURN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Walker Formaldehyde, page 139(1944), Reinhold Pub. Corp., New York.

Certificate of Correction Patent No. 2,527,714

ANDREW P. DUNLOP ET AL. It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 3, line 16, for ilulstration read illustration; column 4, line31, for theated read treated; column 7, line 65, strike out The tubesWere inspected every hour. When any; x

and that the said Letters Patent should be read as correctedabove, sothat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 2nd day of January, A. D. 1951.

October 31, 1950 THOMAS F. MURPHY,

Assistant Uommissioner of Patents.

6. A NEW ARTIFICIAL THERMOSETTING RESIN COMPRISING THE PRODUCT OFCONDENSATION UNDER ACIDIC CONDITIONS OF A COMPOUND OF THE CLASSCONSISTING OF FORMALDEHYDE, COMPOUNDS WHICH ENGENDER FORMALDEHYDE ANDGLYOXAL WITH A FURYLETHYLENE DERIVATIVE CORRESPONDING TO THE GENERALFORMULA